I am going to discuss two ways, both ways required you to setup a bit of jQuery code in your template initially. Where the ways differ is that in the second way, you have to EDIT HTML of your content (post or page).

Both of the ways, require jQuery, those one with good JS understanding can implement this without jQuery.

Method One:

First of all, go to the Template menu and then go to Edit HTML to edit the HTML of your template.

This will bring up the code editor, then, find the <data:post.body/>

PLEASE NOTE: It can be that you have multiple <data:post.body/> in your template. If you do not know which one is the actual one working then please read the following post to find out or simply watch the following video tutorial first.

ContentMiddleAd

Please note:

Notice the value of the variable theInsideContentAd. This is the ad code that will be placed. You have to escape your ad code to become a JS string. You can use this tool Code to JS String, copy & paste your adsense ad code there and click on JS String, you will get the JS string of your ad code there. Use that JS string as the value of the InsideContentAd.

So from now on, whenever you are editing or writing a new post, write ContentMiddleAd at the place where you want to show the ad in the content and then do the following

Select the text ContentMiddleAd

First click on the Remove Formatting button of your editor. (see the following image) This will remove unnecessary tags or style attributes

Then click on the Format dropdown and select Heading. This will wrap the text in <h2 />

That's it, you are done. Try it. And let me know if there is any issue implementing. You can watch the following video on this tutorial